FERRO CEMENT

BUILDING TECHNOLOGY AND MANAGEMENT

Definition

“Ferro cement is a type of thin wall

reinforced concrete, commonly constructed

of hydraulic cement mortar, reinforced with

closely spaced layers of continuous and

relatively small size wire mesh. The mesh

may be made of metallic or other suitable

materials”

-ACI Committee 549, 1980

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• Cement mortar is reinforced with layers of

continuous and small diameter wire meshes

• Mortar provides the mass and wire mesh

imparts tensile strength and ductility

• Italian engineer Pier Liugie Nervi is credited

with inventing ferro cement in the 1940’s

Ferro cement

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Materials used in Ferro cement

• Cement mortar mix

• Skeleton steel

• Steel mesh reinforcement or Fibre-

reinforced polymeric meshes

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Typical section of Ferro cement

Cement mortar mix

• OPC and fine aggregate matrix is used

• The matrix constitutes 95% of the

composite and governs its behavior

• FA (sand), occupies 60 to 75% of the volume

of the mortar

• Plasticizers and other admixtures are used

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Mix Proportions

• Sand: cement ratio (by mass) 1.5 to 2.5

• Water: cement ratio (by mass) 0.35 to 0.60

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Skeleton steel

• Forms the skeleton of the structure

• 3 to 8 mm steel rods are used

• Used in the form of tied reinforcement or

welded wire fabric

• Used to impart structural strength in case

of boats, barges etc

• Reinforcement should be free from dust,

rust and other impurities

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Steel mesh reinforcement

• Consists of galvanized steel wires of

diameter 0.5 to 1.5 mm, spaced at 6 to

20mm centre to centre

• Available as woven/interlocking mesh and

welded mesh

• Welded wire mesh has hexagonal or

rectangular openings

• Expanded-metal lath is also used

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Types of Wire Meshes

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Chicken wire mesh

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Expanded Metal Lath

Fibre-reinforced Polymeric meshes

Made from carbon, glass etc.

Advantages:

I. High corrosion resistance

II. High strength

III. Lower unit weight

IV. Easy to handle

V. Good fatigue behavior

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Disadvantages:

I. High cost

II. Low shear strength

III. Low ductility

IV. Susceptibility to stress rupture failure

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Fibre-reinforced Polymeric meshes

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Typical cross-sections of Ferro cement(Source: Naaman 1999)

Ferro cement Construction

• Container for water treatment

Container for water treatment.flv

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Behavior of Ferro cement in Tension

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RC in tension Ferro cement in tension

(Source: Naaman 1999)

Advantages of Ferro cement

• High ductility

• High resistance to cracking width

• Ability to undergo large deflection

• Improved impact resistance and toughness

• Good fire resistance

• Good impermeability

• Low strength to weight ratio

• Low maintenance costs

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Construction Methods for Ferro cement

• Skeletal Armature Method

• Closed Mould Method

• Integral Mould Method

• Open Mould Method

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Skeletal Armature Method

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(Source: Naaman 1999)

Closed Mould Method

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(Source: Naaman 1999)

Integral Mould Method

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(Source: Naaman 1999)

Integral mould

• C:\Users\CIVIL\Downloads\video (1).flv

• C:\Users\CIVIL\Downloads\video (2).flv

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Open Mould Method

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(Source: Naaman 1999)

Applications of Ferro cement

• Marine applications

• Water supply and sanitation

• Agricultural

• Residential buildings

• Rural energy

• Other structures

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1. Marine Applications

• Boats, fishing vessels, barges, cargo tugs,

catamarans, yachts and flotation buoys

• Key criteria for marine applications: light

weight, impact resistance, thickness and

water tightness

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27Boat with Ferro-cement hull

2. Water supply and sanitation

Water tanks, sedimentation tanks, swimming

pool linings, well casings, septic tanks etc.

3. Agricultural

Grain storage bins, silos, canal linings, pipes,

shells for fish and poultry farms

4. Residential Buildings

Houses, community centers, precast housing

elements, corrugated roofing sheets, wall

panels etc.28

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Ferro cement structure for roofing

5. Rural Energy

Biogas digesters, biogas holders,

incinerators, panels for solar energy

collectors etc.

6. Other structures

Bus shelters, industrial shelters, pedestrian

bridges, skateboard rings, sculptures etc.

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Reference

o Naaman, AE, Ferrocement & Laminated

Cementitious Composites, Techno Press

3000

o Santhakumar, AR, Concrete Technology,

Oxford University Press

o Gambhir, ML, Concrete Technology: Theory

and Practice, McGraw Hill

o Shetty, MS, Concrete Technology, S Chand

Publishers